This invention relates to an arrangement for controlling the movement of an angularly movable member, and has particular application to devices for controlling the movement of a wing, such as a door. Such devices include overhead door closers and floor springs.
An object of the invention is to provide an arrangement for controlling the movement of an angularly movable member in an effective manner.
According to the invention, there is provided a control mechanism for use with an angularly movable shaft, the control mechanism comprising:
a torsion spring, the shaft being positioned within the torsion spring; and
a retarding means for tightening the torsion spring about the shaft, the tightening of the torsion spring retarding the angular movement of the shaft.
Preferably the retarding means of the control mechanism moves a free end of the torsion spring to tighten the torsion spring about the shaft.
Conveniently the retarding means comprises:
a strap connected to the shaft;
a movable hydraulic piston connected to the strap, the piston normally holding the strap in tension relative to the torsion spring, the strap, when in tension, preventing the torsion spring from tightening about the shaft.
Desirably the shaft includes a first portion having a circular cross-sectional shape, the torsion spring being positioned about the first portion, and a second portion having a shaped cam surface to vary the output torque, the strap being connected to the second portion.
More preferably the retarding means comprises:
a linkage mechanism connected to one end of the torsion spring, the linkage mechanism being movable from a normal position to a retarding position, the movement of the linkage mechanism from the normal position to the retarding position tightening the torsion spring about the shaft.